Fire Interactions and Pulsation - Theoretical and Physical Modeling
Fire Interactions and Pulsation - Theoretical and Physical Modeling
复制标题
火灾相互作用和脉动 - 理论和物理建模
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
Trevor B. Maynard
中科院分区：
文献类型：
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作者：
Trevor B. Maynard
火灾行为的研究有许多应用，从控制破坏性野火到设计更高效的内燃机。自由燃烧火焰的两种现象，即火脉动和火焰相互作用，对于理解和控制火灾具有重大影响。火脉动是自由燃烧火焰的一个特征，其特征是火焰结构的周期性、大规模波动，其似乎仅取决于火的规模。为了帮助了解这些脉动的起源，使用高速摄像机拍摄了层流和湍流池火灾。对整个脉动周期中发生的图像强度波动进行定量分析，以确定主要脉动频率的存在。测量的脉动频率与文献中的现有实验非常吻合。该图像还用于支持一个新的理论模型，该模型提出脉动最初是由热气流触发的，离散对流不稳定性在上升并扰乱火焰结构之前在火焰底部形成。当两个或多个火焰彼此相邻放置时，就会发生火灾相互作用。据观察，随着邻近火势的汇聚，火焰高度、倾斜角度、燃烧强度和蔓延速度都会增加。为了解释火焰倾斜现象，建立了基于线性动量守恒的模型，并表明火焰之间的内部区域的夹带由于火焰构型而受到限制。通过使用互相关图像分析来分析放置在两个固定池火灾的夹带场中的被动示踪剂烟雾的行为，对该模型进行了验证。此外，还详细讨论了火焰合并的传热方面，并提出了对现有火灾蔓延模型进行修改以适应相邻火焰前锋的建议。
The study of fire behavior has numerous applications, from the control of destructive wildfires to the design of more efficient combustion engines. Two phenomena of freely burning flames, fire pulsation and flame interaction, have significant consequences for the understanding and control of fire.Fire pulsation is a feature of freely burning flames, and is characterized by periodic, large scale fluctuations in flame structure which appear to be only dependent on the scale of the fire. To help understand the origins of these pulsations, both laminar and turbulent pool fires were filmed using a high speed camera. Fluctuations in image intensity, which occur throughout the pulsation cycle, were quantitatively analyzed to identify the existence of dominant pulsation frequencies. The measured pulsation frequencies agreed well with existing experiments from the literature. The imagery was also used to support a new theoretical model which proposes that pulsation is initially triggered by thermals, discrete convective instabilities which develop at the base of the flame before rising and disturbing the flame structure.Fire interactions occur when two or more flames are placed adjacent to each other. Flame height, angle of tilt, burning intensity, and rate of spread have all been observed to increase as proximate fires converge. To explain the flame tilting phenomena, a model based on the conservation of linear momentum is developed, and it is shown that entrainment in the inner region between flames is restricted as a result of flame configuration. The model is validated by using cross-correlation image analysis to analyze the behavior of passive tracer smoke placed in the entrainment field of two stationary pool fires. In addition, the heat transfer aspects of flame merging are discussed in detail, and modifications to existing fire spread models to accommodate an adjacent flame front are proposed.